What is a Metering Device – Refrigeration Components

What is a Metering Device – Refrigeration Components

What you will learn from What is a Metering Device:
1) We will answer the question, “What is a metering device” by defining the various types of HVAC equipment that use different types of metering devices and why.
2) How the metering device is involved in the refrigeration cycle
3) A comprehensive list of metering devices defining the metering devices commonly used in HVAC
4) Lots of resource and related links to help you learn more about metering devices.

What is a Metering Device - TXV- Thermostatic Expansion Valve

TXV Metering Device for a Heat Pump

Depending on the type of HVAC air conditioning or heat pump system it is and the efficiency range of the system will depend on the type of metering device the system has installed by the HVAC manufacturer of the air conditioner or heat pump system. Lower efficiency HVAC air conditioner and heat pump models have fixed orifice types while higher efficiency systems have thermostatic expansion valves installed in the HVAC air conditioner or heat pump system. The thermostatic expansion valve is far more complex than the fixed orifice metering device as the thermostatic expansion valve metering device modulates the refrigerant flow based on the temperature of the refrigerant temperature in the evaporator coil. This allows a specific amount of refrigerant, based on demand, to be metered into the evaporator coil while the fixed orifice metering device allows the same amount of refrigerant to enter the enter the coil no matter the conditions or the demand. As the liquid refrigerant enters the metering device it changes temperature and pressure. A partial amount of the liquid refrigerant flashes into a refrigerant gas or vapor as it leaves the metering device and enters the evaporator coil.


Evaporator Coil for Heat Pumps & Air Conditioners | HVAC Refrigeration

Evaporator Coil for Heat Pumps & Air Conditioners

Old Evaporator Coil in a Rooftop Air ConditionerEvaporator Coil for Heat Pumps & Air Conditioners – the evaporator is responsible for absorbing heat into the coils and the refrigerant. The evaporator is an essential component of vapor compression refrigeration. This is usually done as result of passing air or water over the evaporator coil where a heat exchange process takes place. Heat leaves the air or water (whatever medium is used) and is absorbed into the coil and the liquid refrigerant. As more and more heat is absorbed by the evaporator coil and the refrigerant again changes state from a liquid to a refrigerant vapor. By the time the refrigerant leaves the evaporator coil the refrigerant should be all vapor and ready to be received again by the refrigeration compressor. (more…)

The Condenser for Air Conditioners and Heat Pumps| HVAC Refrigeration

The Condenser for Air Conditioners and Heat Pumps - Trane Heat Pump Condenser

Trane Heat Pump Condenser

The Condenser for Air Conditioners and Heat Pumps

The condenser coil receives the high pressure high temperature refrigerant vapor from the compressor and immediately begins to remove heat from the refrigerant vapor. As the refrigerant vapor makes its way through the condenser coil more and more heat is removed and the refrigerant vapor changes state from a refrigerant vapor to a refrigerant liquid. While the liquid refrigerant changes temperatures from a higher temperature to a slightly lower temperature the pressure remains constant. As the refrigerant vapor leaves the condenser coil it makes it way to the metering device. (more…)

HVAC Centrifugal Compressors | HVAC Refrigeration

HVAC Centrifugal Compressors

McQuay Chiller Uses HVAC Centrifugal Compressors

HVAC Centrifugal Compressors – Centrifugal compressors are used in many applications including pipeline transport of natural gas along with many other related applications including vapor compression refrigeration. These compressors have different operating limitations than the reciprocating compressor, the scroll compressor, and the rotary compressor. They an operating range where it operates efficiently however outside of this range, either the over or under that operating range, is basically useless. Other issues make them not ideal for use in certain applications because of the operating range issues. (more…)

Rotary Compressors | Air Conditioning & Heating Systems

Rotary Compressors

Rotary Compressors – The rotary compressor used in HVAC applications for air conditioning and heating systems offer some of the most efficient air conditioner and heat pump systems one can find on the market. Despite the rotary compressor being a key component of an air source air conditioner or heat pump the efficiency offered by this compressor when used as a modulating compressor can exceed efficiency ratings of some geothermal systems. When the compressor is coupled with an inverter and the proper inverter control system the efficiency of the air source air conditioner or heat pump system spike to match those of some geothermal air conditioner or heat pump systems.


Refrigeration for HVAC | Air Conditioning and Heat Pumps

Refrigeration for HVAC

Air conditioners and heat pumps use the process of refrigeration to provide heating and cooling. What is the definition of the process of refrigeration? Refrigeration is the process of moving heat and depending on whether it is a heat pump or air conditioner and what mode it is in will depend where you are moving the heat. An air conditioner and a heat pump (in the cooling mode) will move heat outside. The evaporator coil absorbs the heat and the condenser rejects the heat. (more…)

Ammonia Chilled Water System | Commercial HVAC

Ammonia Chilled Water SystemAmmonia Chilled Water System | Commercial HVAC

This chilled water unit is a new ammonia chiller. This unit is also unique in that it has no compressor. Instead it uses the chemical properties of ammonia and heat from natural gas to condense the refrigerant which is ammonia. A chiller provides chilled water to a chilled water loop. Cold water is circulated through a loop where it is direct into a coil in an air handler. Air is blown across a coil where a heat exchange process takes place. The air handler discharges cool conditioned air throughout a duct system. Chilled water systems are typically used in commercial air conditioning applicationsbut there are some chilled water systems in residential applications. (more…)

Vapor Compression Refrigeration | Refrigeration HVAC

Refrigeration HVAC - Vapor Compression Refrigeration

These compressors are integral to a vapor compression refrigeration system in a supermarket

The process of refrigeration uses the vapor-compression refrigeration cycle to move heat from one place to another. In many HVAC air conditioning and heat pump applications the process of refrigeration or the vapor-compression cycle is what makes it work. This process, in the air conditioning mode, moves heat from inside the structure to the outside. Heat pumps draw heat from the outside even when it is cold and move the heat inside using the vapor-compression cycle or refrigeration. Heats pumps by the way, heat in the winter and cool in the summer but it uses the refrigeration process to accomplish the heating and cooling. The process of refrigeration or vapor-compression cycle in HVAC air conditioning and heat pump applications is a mechanical and chemical process of moving heat from one place where it is not wanted or needed and moving it to another place. (more…)

DX CRAC Unit Condensers | Critical Facility HVAC

DX CRAC Unit CondensersDX CRAC Unit Condensers | Critical Facility HVAC

DX CRAC Unit Condensers | Critical Facility HVAC – Most data centers do not utilize HVAC DX (Direct Expansion) CRAC units or air conditioning but instead use chilled water systems to provide cooling for the data center. In smaller buildings such as remote telecom buildings DX air conditioning systems are used to keep the equipment cool and operating efficiently. A DX CRAC Unit uses vapor compression refrigeration to provide cooling with a chemical refrigerant versus a chilled water system that utilizes chilled water from a chiller. CRAC Units or Computer Room Air Conditioners also serve telecom facilities for telephone services including cellular telephone facilities in remote locations. The CRAC units that serve telecom facilities in remote locations are typically DX CRAC Units that have utility back-up by stand-by generator so that if the utility fails to provide electricity for whatever reason the stand-by generator kicks on and provides power so that the telecom facility can remain on line. (more…)

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